I think I may be the only human alive who not only knows what this is, but is completely uninterested in it! Why? I program for a living, so the last thing on my mind when it comes to music is having to sit down and program some more. The sequencer and twisting a few knobs is more than enough for me. But yes, Max/MSP and Max4Live is a very powerful musical object creator (not just synth creator).

EDIT: $300 smackers, not cheap. The only way I'd get into that, is if there were a ton of cool M4L doodads designed by the community, which I'm sure there will.